Proposed research will further examine the response of hypothalamic monoamine oxidase (MAO) to naturally occurring changes in gonadal hormone levels and explore whether such changes in MAO activity are involved in regulation and/or mediation of female sexual behavior (lordosis). Specific nuclei within the preoptic-hypothalamic area which show hormone-dependent changes in MAO activity and which are implicated as sites for hormonal regulation of lordosis will be sampled and MAO activity measured by radiochemical techniques. Emphasis will be placed on measuring MAO activity during the estrous cycle, after ovariectomy, and after hormone treatment. Mechanisms responsible for the estrogen plus progesterone-dependent increase in MAO will be stuided. The involvement of MAO in lordosis behavior will be examined with monoamine oxidase inhibitors which are known to decrease lordotic responding in hormonally primed ovariectomized rats. Specific inhibitors of Type A and B MAO will be given systemically and by cannula to specific hypothalamic regions and the effects on lordosis measured (lordosis quotient). The application of biochemical, anatomical, pharmacological and behavioral techniques should characterize the role of MAO in hormonally dependent lordosis behavior and the sites in the hypothalamus and mechanisms responsible.